Hemp, History, and Agriculture

More than 150,000 acres of hemp were cultivated as a part of the USDA’s “Hemp for Victory” program during WWII.

The 1937 Marihuana Tax Act defined hemp as a narcotic drug, requiring that farmers growing hemp hold a federal registration and special tax stamp, effectively limiting further production expansion.

The Controlled Substances Act of 1970 (CSA) adopted the same definition of Cannabis sativa that appeared in the 1937 Marihuana Tax Act.

Hemp in American History

In the late 1750’s Virginia government started offering subsidies to help offset poor tobacco prices and encourage international trade. Augusta County farmers jumped at the opportunity to carve out a place for hemp production within their mixed farming routine. The Virginia legislature paid farmers four shillings per hundredweight of hemp harvested, and added two more shillings for each hundredweight shipped to England.

The incentive was tailor made for the Valley farmers who had come from the north of Ireland and knew fiber production. In Ireland, their main agricultural cash crop came from turning flax into linen. They knew how to grow and process flax and turn this fiber crop into a finished product. The process for turning hemp into a useful fiber was almost identical.

Hemp plants were pulled out by the roots in the fall and laid out in the fields to rot (called rhetting) after being repeatedly wet by the weather. The process, which took as long as three months, broke down the gums and hard outside layers of the plant stems to reveal the inner fibers.

Once this was finished, the plants were broken on a wooden break. At this point the hemp was called gross hemp and was sometimes sold at this stage for someone else to process further into rope or cloth. However most Valley farmers took the processing at least one step further and scutched their hemp to remove all of the pieces of bark. The product was now called neat hemp. The final processing stage was called hackling, where the fibers were pulled through a series of metal spikes in order to straighten the long fibers and orient them all in the same direction.

….It took six tons of harvested hemp to produce a ton of marketable hemp. An acre yielded about 500 pounds of hemp

Farming 10,000 Acres of Hemp Will Provide as Much Paper, Building Materials & Pulp as 41,000 Acres of Forest.

— Source: US Dept. of Agriculture USDA Bulletin 404, Published 1916

Pulp & Paper

Paper made of hemp lasts much longer than that made of trees, without cracking, yellowing or otherwise deteriorating: It’s the “archivist’s perfect paper.”

Processing hemp for paper uses far less chemical acid than does wood.

Over a 20 year period, one acre of hemp produces as much pulp as 4.1 acres of forest land.

Fuel

Biomass conversion to fuel has proven economically feasible in laboratory tests and continuous operation of pilot plants since 1973.

It has a heating value of 5000-8000 BTU/lb, with virtually no ash or sulfur produced by combustion.

Hemp, especially the hurds, can be burned as is or processed into charcoal, methanol, methane, or gasoline through pyrolysis (destructive distillation). As with maize, hemp can also be used to create ethanol.

Fiber

The long bark fiber, at 77% cellulose, is cleaned and spun into thread, yarn or rope, or woven or knit into a variety of durable, high-quality textiles for clothing, canvas and fabrics of many textures.

Fabrics made from hemp are stronger, more insulative, more absorbent and more durable than cotton. Natural, organic hemp fiber “breathes” and is biodegradable. With minor retooling, our textile mills can spin and weave hemp fiber as smooth as silk, as tough as burlap, or as intricate as lace.

Erosion Control

The hemp roots anchor and aerate the soil to control erosion and can prevent mudslides.

Building Materials

The inner core of the stalk, called hemp hurd, contains cellulose and can be used for non-toxic paints and sealants; industrial fabrication materials; construction materials; hemi-cellulose for plastic, and and a light weight strong hemp-crete.

Hemp is the temperate climate zone’s most prolific source of plant cellulose: the basic raw material used for plastics, fabrication material, chip-board, fiber board and other construction boards. France makes a concrete substitute from hemp, and Henry Ford once built and powered a car with hemp.

McPartland (1997) reviewed research on the pesticide and repellent applications of Cannabis. Dried plant parts and extracts of Cannabis have received rather extensive usage for these purposes in the past, raising the possibility that research could produce formulations of commercial value.

Livestock Feed

Hemp seed cake makes an excellent feed for animals. Letniak et al. (2000) conducted an experimental trial of hemp as silage. No significant differences were found between yield of the hemp and of barley/oat silage fed to heifers, suggesting that fermenting hemp plants reduces possible harmful constituents.

Hemp as an Agricultural Cross-Pollination Barrier

One of the most curious uses of hemp is as a fence to prevent pollen transfer in commercial production of seeds. Isolation distances for ensuring that seeds produced are pure are considerable for many plants, and often impractical. At one point in the 1980s, the only permitted use of hemp in Germany was as a fence or hedge to prevent plots of beets being used for seed production from being contaminated by pollen from ruderal beets. The high and rather inpenetrable hedge that hemp can produce was considered unsurpassed by any other species for the purpose. As well, the sticky leaves of hemp were thought to trap pollen. However, Saeglitz et al. (2000) demonstrated that the spread of beet pollen is not effectively prevented by hemp hedges. Fiber (i.e. tall) cultivars of hemp were also once used in Europe as wind-breaks, protecting vulnerable crops against wind damage. Although hemp plants can lodge, on the whole very tall hemp is remarkably resistant against wind.

Bioremediation

Preliminary work in Germany (noted in Karus and Leson 1994) suggested that hemp could be grown on soils contaminated with heavy metals, while the fiber remained virtually free of the metals. Kozlowski et al. (1995) observed that hemp grew very well on copper-contaminated soil in Poland (although seeds absorbed high levels of copper). Baraniecki (1997) found similar results. Mölleken et al. (1997) studied effects of high concentration of salts of copper, chromium, and zinc on hemp, and demonstrated that some hemp cultivars have potential application to growth in contaminated soils. It would seem unwise to grow hemp as an oilseed on contaminated soils, but such a habitat might be suitable for a fiber or biomass crop.

Wildlife Uses

Hemp seeds are well known to provide extremely nutritious food for both wild birds and domestic fowl. Hunters and birdwatchers who discover wild patches of hemp often keep this information secret, knowing that the area will be a magnet for birds in the fall when seed maturation occurs. Increasingly in North America, plants are being established to provide habitat and food for wildlife. Hemp is not an aggressive weed, and certainly has great potential for being used as a wildlife plant. Of course, current conditions forbid such usage in North America.

Agronomy

Hemp does best on a loose, well-aerated loam soil with high fertility and abundant organic matter. Well-drained clay soils can be used, but poorly-drained clay soils are very inappropriate because of their susceptibility to compaction, which is not tolerated. Young plants are sensitive to wet or flooded soils, so that hemp must have porous, friable, well-drained soils. Sandy soils will grow good hemp, provided that adequate irrigation and fertilization are provided, but doing so generally makes production uneconomical. Seedbed preparation requires considerable effort. Fall plowing is recommended, followed by careful preparation of a seedbed in the spring. The seedbed should be fine, level, and firm.

Although the seedlings will germinate and survive at temperatures just above freezing, soil temperatures of 8°–10°C are preferable. Generally hemp should be planted after danger of hard freezes, and slightly before the planting date of maize. Good soil moisture is necessary for seed germination, and plenty of rainfall is needed for good growth, especially during the first 6 weeks.

Hemp requires about the same fertility as a high-yielding crop of wheat. Industrial hemp grows well in areas that corn produces high yields. Hemp particularly requires good nitrogen fertilization, more so for seed production than fiber. Adding nitrogen when it is not necessary is deleterious to fiber production, so that knowledge of the fertility of soils being used is very important. Organic matter is preferably over 3.5%, phosphorus should be medium to high, potassium should be medium to high, sulfur good(>5,000 ppm), and calcium not in excess (<6,000 ppm).

Finding cultivars suited to local conditions is a key to success. Oilseed production was a specialty of the USSR, and there is some likelihood that northern regions of North America may find short-season, short-stature oilseed cultivars ideal.

Although hemp can be successfully grown continuously for several years on the same land, rotation with other crops is desirable. A 3- or preferably 4-year rotation may involve cereals, clover or alfalfa for green manure, maize, and hemp. In Ontario it has been recommended that hemp not follow canola, edible beans, soybeans or sunflowers. However, according to Bócsa and Karus (1998), “it matters little what crops are grown prior to hemp.”

For a fiber crop, hemp is cut in the early flowering stage or while pollen is being shed, well before seeds are set. Tall European cultivars have mostly been grown in Canada to date, and most of these are photoperiodically adapted to mature late in the season. Small crops have been harvested with sickle-bar mowers and hay swathers, but plugging of equipment is a constant problem. Hemp fibers tend to wrap around combine belts, bearings, indeed any moving part, and have resulted in large costs of combine repairs Older equipment designed for processing hemp has had to be reverse engineered and there is opportunity for jobs in producing processing equipment. Slower operation of conventional combines has been recommended Large crops may require European specialized equipment, but experience in North America with crops grown mainly for fiber is limited. The Dutch company HempFlax has developed or adapted several kinds of specialized harvesting equipment.